Previously loading the environments index page would show a 500 error
when two conditions were met:

1. The associated cluster deployment had no pods
2. Reactive caching has cached the state of the deployment data.

Previously the filtering of pods by project environment were only run if
there were pods present, but this special case isn't needed as the
filter already handles empty arrays.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/216118